Fix cut'n'paster errors in conditional compilation.  Prevented LM4F120 Launchpad UARTs 2-7 from being used

x86:  fix 'Error: .size expression for idle_stack does not evaluate to a constant' bug from Matt Campbell

Assembler changes with the gcc-47 distribution from ARM mean that we need to be explicit about branch one or more of the wide branch opcodes results in bad table branching.  From Mike Smith

configs/efm32-dk3650: Support for Energy Micro's development kit for the Leopard Gecko MCU.  From Richard Cochran

arch/arm/src/Makefile: dependency directory list is now computed from the VPATH.  From Richard Cochran

Config.mk: If WINTOOL is set, COMPILE definition should convert path generated by Cygwin make to a proper Windows path.  From Richard Cochran (2014-1-23).

You can now specify or override the default board sub-directory.  This is only useful when CONFIG_ARCH_BOARD_CUSTOM is used and the default board sub-directory is not available

Fix all Cortex-M3/4 implementations of up_disable_irq().  They were doing nothing.  Thanks to Manuel Stühn for the tip.

FAT: Fix some root directory logic that was conditionally done only for FAT32.  Apparently this needs to be done for all FAT types.  From Tridge via Lorenz Meier

If write buffering is enabled, then it is necessary to release the write buffer resources (callback structure) when the socket is closed

Add support for the SO_LINGER socket option.  Based on logic from Jason Jiang.  Utestested on initial commit